U.S. patent number 10,349,837 [Application Number 15/863,389] was granted by the patent office on 2019-07-16 for materials and methods for non-invasively measuring temperature distribution in the eye.
This patent grant is currently assigned to THE FLORIDA INTERNATIONAL UNIVERSITY BOARD OF TRUSTEES. The grantee listed for this patent is Yuqiang Bai, Pedro Lopez, Jessica Ramella-Roman, Herbert Wertheim. Invention is credited to Yuqiang Bai, Pedro Lopez, Jessica Ramella-Roman, Herbert Wertheim.
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United States Patent |
10,349,837 |
Ramella-Roman , et
al. |
July 16, 2019 |
Materials and methods for non-invasively measuring temperature
distribution in the eye
Abstract
The present invention provides devices and methods for measuring
the temperature distribution of an eye using non-invasive
techniques. Embodiments of the present invention utilize laser
speckle cross-correlation to determine the thermal distribution of
an eye.
Inventors: |
Ramella-Roman; Jessica (Miami,
FL), Wertheim; Herbert (Miami, FL), Lopez; Pedro
(Miami, FL), Bai; Yuqiang (Miami, FL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Ramella-Roman; Jessica
Wertheim; Herbert
Lopez; Pedro
Bai; Yuqiang |
Miami
Miami
Miami
Miami |
FL
FL
FL
FL |
US
US
US
US |
|
|
Assignee: |
THE FLORIDA INTERNATIONAL
UNIVERSITY BOARD OF TRUSTEES (Miami, FL)
|
Family
ID: |
62782528 |
Appl.
No.: |
15/863,389 |
Filed: |
January 5, 2018 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20180192886 A1 |
Jul 12, 2018 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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62443750 |
Jan 8, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01K
13/00 (20130101); G01K 11/00 (20130101); G01K
13/002 (20130101); A61B 3/0025 (20130101); A61B
3/14 (20130101); G01N 21/4788 (20130101); A61B
5/01 (20130101); A61B 3/10 (20130101); A61B
5/0062 (20130101); G01N 2021/479 (20130101); G01K
2213/00 (20130101) |
Current International
Class: |
A61B
5/01 (20060101); A61B 3/00 (20060101); A61B
5/00 (20060101); G01K 11/00 (20060101); A61B
3/14 (20060101); G01N 21/47 (20060101); A61B
3/10 (20060101); G01K 13/00 (20060101) |
Other References
Aizu, Y., Asakura, T., "Coherent optical techniques for diagnostics
of retinal blood flow." Journal of Biomedical Optics, Jan. 1999,
4(1): Abstract. cited by applicant .
Fercher, A.F., Briers, J.D., "Flow visualization by means of
single-exposure speckle photography." Optics Communications, Jun.
1981, 37(5): Abstract. cited by applicant .
McCally, R.L., et al., "Laser Eye Safety Research at APL." John
Hopkins APL Technical Digest, 2005, 26(1): 46-55. cited by
applicant.
|
Primary Examiner: Dinh; Jack
Attorney, Agent or Firm: Saliwanchik, Lloyd &
Eisenschenk
Claims
We claim:
1. A method for measuring a temperature of an area in an eye,
comprising: a) illuminating the area with a first light beam, b)
receiving a first speckle pattern produced by the first light beam
from the area, c) illuminating the area with a second light beam,
d) receiving a second speckle pattern produced by the first light
beam from the area after illuminating the area with the second
light beam in step c), e) calculating pixel cross-correlation
between the first speckle pattern and the second speckle pattern,
and f) measuring the temperature of the area based on the pixel
cross-correlation determined in step e).
2. The method of claim 1, wherein the area in the eye is
continuously illuminated with the first light beam throughout steps
a) to d).
3. The method, according to claim 1, wherein the eye is a human
eye.
4. The method, according to claim 1, wherein the area in the eye is
in the retina.
5. The method, according to claim 1, wherein the first light beam
and the second light beam have different energies.
6. The method, according to claim 5, wherein the first light beam
has twice the energy compared to the second light beam.
7. The method, according to claim 6, wherein each of the first
light beam and the second light beam has the energy of less than 1
mWatt.
8. The method, according to claim 1, wherein the first light beam
has a wavelength between 650 nm to 750 nm and the second light beam
has a wavelength between 600 nm to 650 nm.
9. The method of claim 1, wherein the first and second speckle
patterns have at least 5.times.5 pixels.
10. The method of claim 9, wherein second light beam has a diameter
of 0.5 mm and the second light beam lasts for 1 millisecond.
11. A method for determining a temperature distribution in an eye,
comprising: a) determining temperatures for a plurality of areas in
the eye according to the method of claim 1, b) determining the
temperature distribution in the eye based on the temperatures of
the plurality of areas in the eye.
12. A laser speckle imaging system, comprising a first laser that
provides a first laser beam and is configured to illuminate an
area, a second laser that provides a pulse second laser beam, a
Galvanometer mirror, which optionally in conjunction with a
dichroic, is configured to illuminate the area with the pulse
second laser beam, and a camera configured to receive speckle
patterns from the area.
13. The laser speckle imaging system of claim 12, wherein each of
the first laser and the second laser is a laser diode and the
camera comprises a polarizer and a 50 mm fl, F#1.3 lens.
14. The laser speckle imaging system of claim 12, wherein the first
laser is configured to emit the first beam of a wavelength between
650 nm to 750 nm and the second laser is configured to emit the
second beam of a wavelength between 600 nm to 650 nm.
15. The laser speckle imaging system of claim 14, further
comprising a processing apparatus, wherein the processing apparatus
receives from the camera the data corresponding to: a first light
speckle pattern produced by a first illumination of a surface by a
first light beam emitted by the first laser and a second light
speckle pattern produced by a second illumination of the surface by
a second light beam emitted by the first laser, wherein between the
first and the second illuminations of the surface by the first
laser the surface is illuminated by a pulse second beam emitted by
the second laser, and wherein the processing apparatus compares the
first light speckle pattern with the second light speckle pattern
and provides the temperature of the surface.
16. The laser speckle imaging system of claim 15, wherein the
illuminated surface is in a subject's retina and the laser speckle
imaging system is configured to position the subject in a manner
that the first and the second laser beams are projected onto the
subject's retina.
17. A method for measuring a temperature of an area, comprising: a)
illuminating the area with a first light beam, b) receiving a first
speckle pattern produced by the first light beam from the area, c)
illuminating the area with a second light beam, d) receiving a
second speckle pattern produced by the first light beam from the
area after illuminating the area with the second light beam in step
c), e) calculating pixel cross-correlation between the first
speckle pattern and the second speckle pattern, and f) measuring
the temperature of the area based on the pixel cross-correlation
determined in step e).
18. The method, according to claim 17, wherein the first light beam
and the second light beam have different energies.
19. The method, according to claim 17, wherein the first light beam
has twice the energy compared to the second light beam.
20. The method, according to claim 17, wherein the first light beam
and the second light beam has energy of less than 1 mWatt.
Description
BACKGROUND OF INVENTION
Sources such as the sun or lasers used in clinical settings can
induce changes in temperature in the eye. The retina can suffer
irreversible damages if exposed to heat out of physiological range
(>37.degree. C.). Current retinal temperature measurement
modalities for animals are limited to invasive techniques. However,
such invasive techniques cannot be generally utilized to measure
the temperature distribution of the eye.
BRIEF SUMMARY
The present invention provides devices and methods for measuring
the temperature distribution of an eye, particularly, the retina,
using non-invasive techniques. The devices and methods can be used,
for example, to assess the pathophysiological rate of ambient
light-induced retinal temperature elevation.
In specific embodiments, the present invention utilizes laser
speckle cross-correlation techniques.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1A is an original retina fundus image showing the vasculature
of a healthy volunteer.
FIG. 1B is a filtered version of the retina image of FIG. 1A
showing the vasculature of a healthy volunteer.
FIG. 1C is a realized phantom of FIG. 1A on an absorbing and
scattering epoxy layer (divisions on the right hand side are in
mm).
FIG. 2 is an image of a speckle imaging system according to an
embodiment of the present invention.
FIG. 3 is a graph of correlation coefficients versus time, showing
speckle cross-correlation with a temperature dependent model.
FIG. 4 shows modeling heat distribution in the eye. Heat spots in
eye can influence the temperature in other areas. A localized
change in retinal temperature induced an asymmetric temperature
distribution in the eye. External temperature measurement (FLIR)
cannot be used to determine retinal temperature differences.
FIG. 5 provides an embodiment of the laser speckle imaging system.
As the temperature of the hot plate increases, the LSI system's
coherent light source illuminates the metallic rod's surface. The
light source produces a speckle pattern on the rod and a stack of
images of the speckle pattern are acquired using software (Matlab,
Natick, Mass.). Any change of the material property, due to heat,
will decrease the speckle autocorrelation.
FIG. 6 provides a close-up view of sample with laser beam. White
arrow and paper corner denote start of vertical separation between
insulated and non-insulated parts of rod.
FIG. 7 shows insulated and not insulated areas of the metal rod.
Isolation (electrical tape) is placed beneath rod before
imaging.
FIG. 8 shows pixel cross-correlation. Pixel cross-correlation was
calculated on each frame of the image stack over time.
FIG. 9 shows effects of temperature on cross-correlation plots. As
the temperature increases from 30.degree. C. to 42.degree. C., an
exponential decay occurs in both cross-correlation plots. The
non-insulated rod shows faster decorrelation than the insulated
rod.
FIG. 10A shows raw speckle image showing insulated [left] and
non-insulated [right].
FIG. 10B shows cross correlation of image stack showcasing the
difference in fitting parameter between both sides. The
non-insulated side shows faster decorrelation.
FIG. 11 shows schematic representation of an exemplary laser
speckle imaging system of the invention that could be used to
determine temperature of a portion of the retina or of the entire
retina.
DETAILED DISCLOSURE
The present invention provides devices and methods for measuring
the temperature distribution of an eye of a subject using
non-invasive techniques. In one embodiment the method of the
invention measures the temperature distribution of the retina. The
determination of the temperature distribution can be used in the
diagnosis, and/or monitoring the progression of, an ocular
pathology. In certain embodiments a confirmatory diagnostic
procedure can also be performed. Optionally, treatment for the
ocular disorder can be administered.
In preferred embodiments, the subject is a mammal, such as, for
example, a human, a dog, a cat, cattle, or a horse.
Conditions that currently have no treatment such a nonexudative
age-related macular degeneration (geographic atrophy) can be caused
by changes in eye temperature. In accordance with the current
invention, diagnostic prediction of age related macular
degeneration can be readily provided accurately and quickly by, for
example, an ophthalmologist.
The basic method for determining retinal temperature according to
the present invention is to observe speckle contrast created by a
coherent light source. Under proper conditions, a rough surface (a
surface with RMS surface height variation that is large with
respect to the laser light wavelength) being illuminated by a
coherent light source will produce a speckle pattern. Any change in
the material properties of the surface, including a change in
temperature, will decrease speckle cross-correlation. This approach
can be used to measure the temperature at specific locations (X, Y)
throughout the retina.
More specifically, a first speckle pattern originating from a
portion of the retina can be obtained by projecting a first beam
onto the portion of the retina. A speckle size of at least
5.times.5 pixels is preferred. The speckle pattern is dependent on
local optical properties and temperature and can have a wavelength
of about 700 nm, in a range from 600 nm to 800 nm, or more
specifically in a range from 650 nm to 750 nm (with a power that is
preferably at or below 1 mWatt). The speckle pattern can then be
altered by applying a short pulse of a second laser onto the
portion of the retina while the first beam is continuously
illuminating the portion of the retina. The second beam can have a
wavelength of about 633 nm, or a range from 575 nm to 675 nm, or
more specifically a range from 600 nm to 650 nm (with a power that
is preferably at or below 1 mWatt). A second speckle pattern
originating from the portion of the retina resulting from the first
beam after the pulse of the second beam is then obtained. Speckle
cross-correlation between the first speckle pattern and the second
speckle pattern is then measured, and the temperature decay after
the pulse second laser can be used to measure the temperature of
the portion of the retina.
In some embodiments, the first and the second beams are scanned
through different locations in the retina to measure temperatures
in multiple locations in the retina. For example, beams can be
scanned throughout the entire retina to determine the temperatures
throughout the entire retina.
Another embodiment of the present invention includes applying two
or more laser pulses onto the retina as the second beams. The first
beam and the second beam can have different energy levels. For
example, the first beam can have twice the energy of the second
beam, and then the ground temperature of the retina can be
measured. The laser can be aligned co-axially with the speckle
illumination. According to the techniques disclosed herein, a
speckle fundus imager can be fabricated to obtain real time imagery
of the retina including temperature data.
Embodiments of the present invention can incorporate the use of
laser speckle cross-correlation technology. Speckle based
techniques can be used to measure very subtle changes in the index
of refraction within a medium.
Data acquisition can be done by, for example, illuminating a retina
with a coherent light (or electromagnetic radiation) source and
imaging the retina with a CCD camera. This exploits the
relationship between camera integration time and speckle lifetime.
If the speckle lifetime is short compared to integration time, the
contrast will be diminished. Furthermore, calculation of localized
speckle contrast allows for the determination of speckle lifetime
and velocity, which is inversely related to speckle lifetime.
A speckle-based imaging system according to the present invention
can include a camera, an imaging system, and computer software and
hardware that analyze the data captured by the imaging system.
Accordingly, certain embodiments of the invention provide a method
for measuring a temperature of an area, comprising:
a) illuminating the area with a first light beam,
b) receiving a first speckle pattern produced by the first light
beam from the area,
c) illuminating the area with a second light beam,
d) receiving a second speckle pattern produced by the first light
beam from the area after illuminating the area with the second
light beam in step c),
e) calculating pixel cross-correlation between the first speckle
pattern and the second speckle pattern, and
f) measuring the temperature of the area based on the pixel
cross-correlation determined in step e).
In some embodiments, the area is continuously illuminated with the
first light beam throughout steps a) to d). In such embodiments,
during step c), the area is illuminated with both the first beam
and the second beam and in step d), the area is only illuminated
with the first beam. In specific embodiments, step d) of receiving
the second speckle pattern is performed between about 0.5
milliseconds (msec) to about 5 msec after step b), preferably,
after about 0.75 msec to about 3 msec after step b), more
preferably, between about 1 msec to 2 msec after step b), and even
more preferably, about 1 msec after step b). As such, step c) can
be performed for about 0.5 milliseconds (msec) to about 5 msec,
preferably, for between about 0.75 msec to about 3 msec, more
preferably, for between about 1 msec to 2 msec, and even more
preferably, for about 1 msec.
In certain embodiments, the methods of the invention are used to
determine the temperature of a surface in an eye of a subject,
particularly, a human eye. Therefore, certain embodiments of the
invention provide a method for measuring a temperature of an area
in an eye, comprising the steps a) to f) described above.
The first light beam and the second light beam can have different
energies. Preferably, the first light beam has twice the energy
compared to the second light beam. Even more preferably, each of
the first light beam and the second light beam has the energy of
less than 1 mWatt.
The first light beam and the second light beam can also have
different wavelengths. For example, the first light beam can have a
wavelength between 600 nm to 800 nm, particularly, 650 nm to 750
nm, and more particularly, about 700 nm. The second light beam can
have a wavelength between 600 nm to 650 nm, particularly, about 625
nm, and more particularly, about 633 nm.
The first and/or the second light beam can have a diameter of 0.5
mm and the first and/or the second light beam lasts for 1 about
millisecond.
In some embodiments, the first light beam has a large diameter
encompassing the whole retina. The speckle pattern includes many
speckles with each speckle at least 3.times.3 pixels, preferably,
5.times.5 pixels.
In some embodiments, the first and second speckle patterns have
3.times.3 to 7.times.7 pixels, preferably, 4.times.4 to 8.times.8
pixels, more preferably, 5.times.5 to 7.times.7 pixels, and even
more preferably, 5.times.5 pixels or 6.times.6 pixels.
The method of determining a temperature of a surface within an eye
according to the invention can be extrapolated to determine the
temperature distribution in an eye, particularly, in a human eye.
As such, the invention provides a method for determining a
temperature distribution in an eye, comprising: a) determining
temperatures for a plurality of areas in the eye according to the
method for measuring a temperature of an area in an eye,
comprising: i) illuminating the area with a first light beam, ii)
receiving a first speckle pattern produced by the light beam from
the area, iii) illuminating the area with a second light beam, iv)
receiving a second speckle pattern produced by the light beam from
the area, v) calculating pixel cross-correlation between the first
speckle pattern and the second speckle pattern, and vi) measuring
the temperature of the area in the eye based on the pixel
cross-correlation determined in step v); and b) determining the
temperature distribution in the eye based on the temperatures of
the plurality of areas in the eye.
In some embodiments, the area is continuously illuminated with the
first light beam throughout sub-steps i) to iv) of step a). In such
embodiments, during sub-step iii), the area is illuminated with
both the first beam and the second beam and in sub-step iv), the
area is only illuminated with the first beam. In specific
embodiments, step iv) of receiving the second speckle pattern is
performed between about 0.5 msec to about 5 msec after step ii),
preferably, after about 0.75 msec to about 3 msec after step ii),
more preferably, between about 1 msec to 2 msec after step ii), and
even more preferably, about 1 msec after step ii). As such, step
iii) can be performed for about 0.5 milliseconds (msec) to about 5
msec, preferably, for between about 0.75 msec to about 3 msec, more
preferably, for between about 1 msec to 2 msec, and even more
preferably, for about 1 msec.
Further embodiments of the invention provide an apparatus for
performing the methods of the invention. In certain such
embodiments, the invention provides a laser speckle imaging system,
comprising a coherent light source, a camera, and a polarized
single mode fiber.
The coherent light source can be a laser diode. The laser diode can
emit a light having a wavelength between 600 to 800 nm,
particularly, about 625 nm, 650 nm, 675 nm, 700 nm, 725 nm, 750 nm,
775 nm, or 800 nm.
The camera can comprise a polarizer and a lens, particularly, a 50
mm fl, F#1.3 lens. Lenses can be incorporated into the imaging
system to filter and magnify light coming from the eye or retina.
For optimal results, a resolution of up to, or greater than, 5, 6,
7, 8, or 9 .mu.m/pixel is preferred.
In some embodiments, the laser speckle imaging system comprises a
first laser that provides a first laser beam to an area to be
illuminated, a second laser that provides the pulse second laser
beam, a Galvanometer mirror, which optionally in conjunction with a
dichroic, deflects the pulse second laser beam to the area. In
certain embodiments, the area to be illuminated is on a plate.
In some embodiments, the area to be illuminated is a subject's
retina. In such embodiments, the laser speckle imaging system is
designed so that a subject can be positioned in a manner that the
first and the second laser beams can be projected onto the
subject's retina.
The laser speckle imaging system can further comprise a processing
apparatus. Typically, a processing apparatus comprises a
microprocessor, storage, bus system, and at least one user
interface element, optionally with user input. The user interface
element can be chosen from a display, a keyboard, and a mouse. In
some embodiments, the system comprises at least one integrated
circuit and/or at least one semiconductor.
The processing apparatus receives from the camera the data
corresponding to: a first light speckle pattern produced by a first
illumination of a surface by a first light beam emitted by the
coherent light source and a second light speckle pattern produced
by a second illumination of the surface by a second light beam
emitted by the coherent light source. The processing apparatus then
compares the first light speckle pattern with the second light
speckle pattern and provides the temperature of the surface.
Acquisition and analysis software can be custom fabricated using a
variety of commercially available tools (e.g., Matlab, Natick,
Mass.).
In certain embodiments, in the laser speckle imaging system of the
coherent light source is configured to illuminate a surface of an
eye. In certain other embodiments, in the laser speckle imaging
system, the camera is configured to receive light speckle pattern
from the surface of the eye. Such laser speckle imaging system can
be used to determine temperature of an area within an eye of a
subject, particularly, a human eye.
The laser speckle imaging system of the invention configured to
illuminate and image a surface of an eye can be used to determining
a temperature of an area in an eye. Such method comprises:
a) illuminating the area with a first light beam,
b) receiving a first speckle pattern produced by the first light
beam from the area,
c) illuminating the area with a second light beam,
d) receiving a second speckle pattern produced by the first light
beam from the area after illuminating the area with the second
light beam in step c),
e) calculating pixel cross-correlation between the first speckle
pattern and the second speckle pattern, and
f) measuring the temperature of the area based on the pixel
cross-correlation determined in step e).
In some embodiments, the area is continuously illuminated with the
first light beam throughout steps a) to d). In such embodiments,
during step c), the area is illuminated with both the first beam
and the second beam and in step d), the area is only illuminated
with the first beam. In specific embodiments, step d) of receiving
the second speckle pattern is performed between about 0.5 msec to
about 5 msec after step b), preferably, after about 0.75 msec to
about 3 msec after step b), more preferably, between about 1 msec
to 2 msec after step b), and even more preferably, about 1 msec
after step b). As such, step c) can be performed for about 0.5
milliseconds (msec) to about 5 msec, preferably, for between about
0.75 msec to about 3 msec, more preferably, for between about 1
msec to 2 msec, and even more preferably, for about 1 msec.
The first light beam and the second light beam have different
energies. Preferably, the first light beam has twice the energy
compared to the second light beam. Even more preferably, each of
the first light beam and the second light beam has the energy of
less than 1 mWatt, for example, below 0.9, 0.8, 0.7, 0.6, or 0.5
mWatt.
The first light beam and the second light beam can also have
different wavelengths. For example, the first light beam can have a
wavelength between 600 nm to 800 nm, particularly, 650 nm to 750
nm, and more particularly, about 700 nm. The second light beam can
have a wavelength between 600 nm to 650 nm, particularly, about 625
nm, and more particularly, about 633 nm.
The first and/or the second light beam can have a diameter of 0.5
mm and the first and/or the second light beam lasts for 1 about
millisecond.
The first and second speckle patterns have 3.times.3 to 7.times.7
pixels, preferably, 4.times.4 to 8.times.8 pixels, more preferably,
5.times.5 to 7.times.7 pixels, and even more preferably, 5.times.5
pixels or 6.times.6 pixels.
An example of using the laser speckle imaging system to capture
retinal images is described in FIGS. 2 and 5. Examples of retinal
phantoms captured using an embodiment of the present invention is
represented in FIG. 1.
Definitions
As used herein, the singular forms "a", "an" and "the" are intended
to include the plural forms as well, unless the context clearly
indicates otherwise. Further, to the extent that the terms
"including", "includes", "having", "has", "with", or variants
thereof are used in either the detailed description and/or the
claims, such terms are intended to be inclusive in a manner similar
to the term "comprising."
The phrases "consisting essentially of" or "consists essentially
of" indicate that the claim encompasses embodiments containing the
specified materials or steps and those that do not materially
affect the basic and novel characteristic(s) of the claim.
The term "about" means within an acceptable error range for the
particular value as determined by one of ordinary skill in the art,
which will depend in part on how the value is measured or
determined, i.e., the limitations of the measurement system. Where
particular values are described in the application and claims,
unless otherwise stated the term "about" meaning within an
acceptable error range for the particular value should be assumed.
In the context of compositions containing amounts of ingredients
where the term "about" is used, these compositions contain the
stated amount of the ingredient with a variation (error range) of
0-10% around the value (X.+-.10%).
In the present disclosure, ranges are stated in shorthand, to avoid
having to set out at length and describe each and every value
within the range. Any appropriate value within the range can be
selected, where appropriate, as the upper value, lower value, or
the terminus of the range. For example, a range of 0.1-1.0
represents the terminal values of 0.1 and 1.0, as well as the
intermediate values of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and
all intermediate ranges encompassed within 0.1-1.0, such as
0.2-0.5, 0.2-0.8, and 0.7-1.0.
When ranges are used herein, combinations and sub-combinations of
ranges (e.g., subranges within the disclosed range), specific
embodiments therein are intended to be explicitly included.
As used herein the phrase "pixel cross-correlation" between a first
speckle pattern and a second speckle pattern represents the
difference in speckle patterns. Such differences include
differences in the pixel locations, pixel intensity, pixel number,
etc.
A greater understanding of the present invention and of its many
advantages may be had from the following examples, given by way of
illustration. The following examples are illustrative of some of
the methods, applications, embodiments and variants of the present
invention. It is, of course, not to be considered as limiting the
invention. Numerous changes and modifications can be made with
respect to the invention.
Example 1
A laser speckle imaging system was constructed to measure the
temperature of retinal phantoms, as shown in FIG. 1. The system can
be seen in the image of FIG. 2. The system included a 12-bit,
monochrome camera (Pantera.RTM. TF 1M60, Dalsa, Ontario, Canada)
with 1024.times.1024 resolution, and maximum frame rate of 60 Hz. A
50 mm focal length F#1.3 lens (Precise Optics, Bay Shore N.Y.) was
used with the camera for magnification and to obtain resolutions of
up to 7 .mu.m/pixel. The light source was a 640 nm, 200 mW diode
laser (Melles Griot, Longmont, Colo.), connected to a single mode
fiber.
Acquisition was conducted automatically with custom software
(Matlab, Natick, Mass.). The laser acted as a coherent light source
and the camera was used to observe speckle contrast. Based on the
speckle contrast measurements, the temperature at specific
locations (X, Y) throughout the retina was determined. A speckle
size of at least 5.times.5 pixels was utilized. The speckle pattern
was then altered by applying a short pulse of laser light onto the
retina. The pulse of laser light had a diameter of 0.50 mm, a
wavelength of 633 nm, and it lasted for 1 msec. The power applied
by the laser was maintained well below levels that would cause
retinal damage.
Speckle cross-correlation was then measured, and the temperature
decay after the pulse was used to measure the ground state
temperature. Experimental results of this procedure can be seen in
FIG. 3. In the graph of FIG. 3, the speckle cross-correlation was
measured for identical samples (eye mimicking phantoms) that were
brought to three different temperatures (40, 45 and 50 degrees
respectively). The graph of FIG. 3 shows both the means and
standard deviations for each of the experiments. Autocorrelation
techniques were used to form a temperature dependent model using
the experimental data, as seen by the solid lines.
Further analysis was conducted using two laser pulses having
controlled energy. The laser pulses were applied to the retinas.
The first pulse had twice the energy of the second. The ground
temperature of the retina was then measured, which in one test was
23.degree. C.
Example 2
Inverse thermal models, depicting the thermal distribution of the
eye, suggest that local retinal temperature cannot be extrapolated
using standard corneal surface temperature measurements. An LSI
system to measure the micro changes in index of refraction
resulting from an increase of local temperature are provided.
Speckle cross-correlation models are used to highlight changes in
speckle patterns as the temperature changes.
In certain embodiments, the LSI system comprises a monochrome
camera, for example, a 12-bit monochrome camera, a lens, for
example, a 50 mm focal length F#1.3 lens, a diode laser, for
example, a diode laser centered at 640 nm, and a polarized single
mode fiber and preliminary studies relating temperature to speckle
cross correlation. The LSI system can be designed to provide a
non-contact imaging system for clinical use in humans, for example,
measuring temperature measurements of human eye, particularly,
human retina.
In the LSI system described in FIG. 5, as the temperature of the
hot plate increases, the LSI system's coherent light source
illuminates the metallic rod's surface. The light source produces a
speckle pattern on the rod and a stack of images of the speckle
pattern are acquired using software (Matlab, Natick, Mass.). Any
change of the material property, due to heat, will decrease the
speckle autocorrelation.
The difference in cross-correlation based on the temperature is
demonstrated based on the difference between the two portions of an
identical surface having different temperatures. As shown in FIG.
6, one area of a metal rod is heated and another area of the metal
rod is insulated using an electrical tape.
Pixel cross-correlation was calculated over time on each frame of
the image stack arising from the insulated and non-insulated areas
of the metal rod (FIG. 8). As the temperature increases,
exponential decay develops in cross-correlation plots from both the
insulated and non-insulated metal rods. However, the non-insulated
rod shows faster decorrelation than the insulated metal rod (FIG.
9).
The faster decorrelation in the non-insulated metal rod versus the
insulated metal rod is shown in FIGS. 8A and 8B. FIG. 8A shows raw
speckle image of insulated and non-insulated metal rod areas. FIG.
8B shows speckle image decorrelation in the insulated and
non-insulated metal rod areas. The non-insulated metal rod area
exhibits higher speckle image decorrelation. As such, FIGS. 8A and
8B demonstrate that speckle images from a surface having higher
temperature shows faster decorrelation compared to speckle images
from a surface having lower temperature. Therefore, the rate of
decorrelation in speckle images from a surface can be used to
determine the temperature of the surface.
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